linux-kernel - Re: [PATCH bpf-next 0/2] bpf, riscv: use BPF prog pack allocator in BPF JIT

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Date:   Mon, 14 Aug 2023 12:06:53 +0200
From:   Björn Töpel <bjorn@...nel.org>
To:     Puranjay Mohan <puranjay12@...il.com>
Cc:     paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, pulehui@...wei.com,
        conor.dooley@...rochip.com, ast@...nel.org, daniel@...earbox.net,
        andrii@...nel.org, martin.lau@...ux.dev, song@...nel.org,
        yhs@...com, kpsingh@...nel.org, bpf@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next 0/2] bpf, riscv: use BPF prog pack allocator in
 BPF JIT

Puranjay Mohan <puranjay12@...il.com> writes:

>> I get a hang for "test_tag", but it's not directly related to your
>> series, but rather "remote fence.i".
>
> I was seeing some stalls like this even without my series but couldn't
> debug them at that time.

Yeah, I think it's not related to your series -- it's just a good
reproducer. ;-)

>>
>>   | rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
>>   | rcu:        0-....: (1400 ticks this GP) idle=d5e4/1/0x4000000000000000 softirq=5542/5542 fqs=1862
>>   | rcu:        (detected by 1, t=5252 jiffies, g=10253, q=195 ncpus=4)
>>   | Task dump for CPU 0:
>>   | task:kworker/0:5     state:R  running task     stack:0     pid:319   ppid:2      flags:0x00000008
>>   | Workqueue: events bpf_prog_free_deferred
>>   | Call Trace:
>>   | [<ffffffff80cbc444>] __schedule+0x2d0/0x940
>>   | watchdog: BUG: soft lockup - CPU#0 stuck for 21s! [kworker/0:5:319]
>>   | Modules linked in: nls_iso8859_1 drm fuse i2c_core drm_panel_orientation_quirks backlight dm_mod configfs ip_tables x_tables
>>   | CPU: 0 PID: 319 Comm: kworker/0:5 Not tainted 6.5.0-rc5 #1
>>   | Hardware name: riscv-virtio,qemu (DT)
>>   | Workqueue: events bpf_prog_free_deferred
>>   | epc : __sbi_rfence_v02_call.isra.0+0x74/0x11a
>>   |  ra : __sbi_rfence_v02+0xda/0x1a4
>>   | epc : ffffffff8000ab4c ra : ffffffff8000accc sp : ff20000001c9bbd0
>>   |  gp : ffffffff82078c48 tp : ff600000888e6a40 t0 : ff20000001c9bd44
>>   |  t1 : 0000000000000000 t2 : 0000000000000040 s0 : ff20000001c9bbf0
>>   |  s1 : 0000000000000010 a0 : 0000000000000000 a1 : 0000000000000000
>>   |  a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000
>>   |  a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000052464e43
>>   |  s2 : 000000000000ffff s3 : 00000000ffffffff s4 : ffffffff81667528
>>   |  s5 : 0000000000000000 s6 : 0000000000000000 s7 : 0000000000000000
>>   |  s8 : 0000000000000001 s9 : 0000000000000003 s10: 0000000000000040
>>   |  s11: ffffffff8207d240 t3 : 000000000000000f t4 : 000000000000002a
>>   |  t5 : ff600000872df140 t6 : ffffffff81e26828
>>   | status: 0000000200000120 badaddr: 0000000000000000 cause: 8000000000000005
>>   | [<ffffffff8000ab4c>] __sbi_rfence_v02_call.isra.0+0x74/0x11a
>>   | [<ffffffff8000accc>] __sbi_rfence_v02+0xda/0x1a4
>>   | [<ffffffff8000a886>] sbi_remote_fence_i+0x1e/0x26
>>   | [<ffffffff8000cee2>] flush_icache_all+0x1a/0x48
>>   | [<ffffffff80007736>] patch_text_nosync+0x6c/0x8c
>>   | [<ffffffff8000f0f8>] bpf_arch_text_invalidate+0x62/0xac
>>   | [<ffffffff8016c538>] bpf_prog_pack_free+0x9c/0x1b2
>>   | [<ffffffff8016c84a>] bpf_jit_binary_pack_free+0x20/0x4a
>>   | [<ffffffff8000f198>] bpf_jit_free+0x56/0x9e
>>   | [<ffffffff8016b43a>] bpf_prog_free_deferred+0x15a/0x182
>>   | [<ffffffff800576c4>] process_one_work+0x1b6/0x3d6
>>   | [<ffffffff80057d52>] worker_thread+0x84/0x378
>>   | [<ffffffff8005fc2c>] kthread+0xe8/0x108
>>   | [<ffffffff80003ffa>] ret_from_fork+0xe/0x20
>>
>> I'm digging into that now, and I would appreciate if you could run the
>> test_tag on VF2 or similar (I'm missing that HW).
>
> Sure, I will try to run this on the board.
> I will rebase my series(+ the patch from arm64 series) on the latest
> bpf-next tree and try to run it.

Thank you!

> Let me know if I need to add:
> +       select HAVE_EFFICIENT_UNALIGNED_ACCESS if MMU && 64BIT

I usually run with that *on*, for better coverage. 


Björn